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// Copyright 2013 The Flutter Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#pragma once
#include <optional>
#include <string>
#include <vector>
namespace fml {
/// The CPU Affinity provides a hint to the operating system on which cores a
/// particular thread should be scheduled on. The operating system may or may
/// not honor these requests.
enum class CpuAffinity {
/// @brief Request CPU affinity for the performance cores.
///
/// Generally speaking, only the UI and Raster thread should
/// use this option.
kPerformance,
/// @brief Request CPU affinity for the efficiency cores.
kEfficiency,
/// @brief Request affinity for all non-performance cores.
kNotPerformance,
};
/// @brief Request count of efficiency cores.
///
/// Efficiency cores are defined as those with the lowest reported
/// cpu_max_freq. If the CPU speed could not be determined, or if all
/// cores have the same reported speed then this returns std::nullopt.
/// That is, the result will never be 0.
std::optional<size_t> EfficiencyCoreCount();
/// @brief Request the given affinity for the current thread.
///
/// Returns true if successfull, or if it was a no-op. This function is
/// only supported on Android devices.
///
/// Affinity requests are based on documented CPU speed. This speed data
/// is parsed from cpuinfo_max_freq files, see also:
/// https://www.kernel.org/doc/Documentation/cpu-freq/user-guide.txt
bool RequestAffinity(CpuAffinity affinity);
struct CpuIndexAndSpeed {
// The index of the given CPU.
size_t index;
// CPU speed in kHZ
int64_t speed;
};
/// @brief A class that computes the correct CPU indices for a requested CPU
/// affinity.
///
/// @note This is visible for testing.
class CPUSpeedTracker {
public:
explicit CPUSpeedTracker(std::vector<CpuIndexAndSpeed> data);
/// @brief The class is valid if it has more than one CPU index and a distinct
/// set of efficiency or performance CPUs.
///
/// If all CPUs are the same speed this returns false, and all requests
/// to set affinity are ignored.
bool IsValid() const;
/// @brief Return the set of CPU indices for the requested CPU affinity.
///
/// If the tracker is valid, this will always return a non-empty set.
const std::vector<size_t>& GetIndices(CpuAffinity affinity) const;
private:
bool valid_ = false;
std::vector<CpuIndexAndSpeed> cpu_speeds_;
std::vector<size_t> efficiency_;
std::vector<size_t> performance_;
std::vector<size_t> not_performance_;
};
/// @note Visible for testing.
std::optional<int64_t> ReadIntFromFile(const std::string& path);
} // namespace fml